Gromet.



A. C. PRATT.v

GROMET.

APPLlCATlON FILED DEC. 10. 1917.

1 ,294, l 6 l D .7 Patented Feb. 11, 1919.

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GROMET.

Specification of Letters Patent.

Patented Feb... it, 119th Application filed December 10, 1917. SerialNo. 206,568.

To all whom it may concern:

Be 'it known that I, ALPHoNso CoMs'rooK PRA'I'I, a citizen of the UnitedStates, residing at Deep River, in the county of Mid dlesex, State ofConnecticut, have invented certain new and useful Improvements 1nGromets; and I do hereby declare the following to be a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

This invention relates to gromets of the type consisting of a. pluralityof convolutions of a single length of wire, each convolution being woundspirally upon the others and the ends of the piece of wirebeing unitedtogether as by butt welding.

Such gromets are widely used, more particularl in the manufacture of theshoes of automo ile tires of the type known as straight side tires,wherein one of the gromets is incased within the rubber and fabric nearthe base of each of the straight sides.

The distinctive feature of the gromet constituting the present inventionis that the spirals of the several convolutions of the gromet are notwound upon a core. The common practice heretofore followed in themanufacture of gromets has involved the provision of a completeconvolution of straight wire serving as a core, followed by windingsuccessive convolutions spirally upon this core. Usually the gromet hascon sisted of seven convolutions, one constituting the core and siXothers wound spirally upon this core, the spirals of the six outerconvolutions lying side by side. The employment of such a straightconvoluti n constituting a core has been essential h reason of the factthat the outer oonvolutions have been wound spirally by hand and a corewas necessary to sustain the spirals during the winding operation.

The gromet of the present invention is erably made by machinery, inaccordance with a procedure which is distinctive in that the spirals areformed in the wire prior to applying the wire to the gromet, whereas theprocedure heretofore followed in the manufacture of gromets by hand hasinvolved spiraling the wire as an incident to its application to thegromet. By reasonof this different procedure, it is possible to make agromet which is hollow, that is, one

in'which all of the several convolutions of spirally formed wire whichconstitute the gromet lie upon the surface of the gromet. Thus, a grometof substantially circular cross-section can be made correspondingclosely to those heretofore widely used in automobile tires but havingsix convolu trons arranged symmetrically about the axis of a-centralspace, instead of seven convolutions, six arranged symmetrically arounda seventh one constituting a core.

Such a hollow gromet of circular crosssection made as above owtlined maybe subjected to pressure in any suitable manner to cause it to assumethe crosssection of an equilateral triangle, contracting itscrosssectional size by taking up the central space. When the pressingdevices are so applied that the apex of the triangle is at the outerside of the gromet and the inner side of the gromet is one of the fiatsides of the triangle, a gromet is produced which is well adapted foruse in automobile tires. When the hollow gromet of circularcross-section consists of six spirally wound convolutions of a singlelength of wire, the pressing of the gromet to the desired triangularcrosssection causes the wire of. three convolutions to lie side by sideat the base of the triangle on the inner side of the gromet, oneconvolution to take position upon the apex of the triangle and the Wireof the two remaining convolutions to lie between the one at the apex andthe row of three at the base. At regular intervals around thecircumference of the gromet, one convolution succeeds another at theapex of the triangle and at each other point around the surface of thegromet, but the triangular cross-sectional form of the gromet and thegeneral arrangement of the six convolutions constituting this gromet oftriangular form is maintained as above indicated.

An embodiment of the invention is illustrated in the drawing annexedhereto. wherein Figure 1 is a view of the gromet in ele-. vation; Fig. 2is a detail view of a section of the gromet on an enlarged scale; Fig. 3is a cross-sectional view of the hollow gromet of circular form, thatis, the gromet as originally made and before being sub jected topressure; and Fig. at is a. similar cross-sectional view of the grometafter it has been subjected to pressure, the section of Fig. i being theline 33 of Fig. 2, so

asawh the gromet in elevation. It consists of a ring or hoop formed froma plurality of convolutions of wire, the wire ofeach of the severalconvolutions being wound spirally and the two ends'of the wire beingbutt welded together. Preferably, the gromet consists of sixconvolutions of the spirally formed wire, the six convolutions beingarranged concentrically about the axis of-a central space, as indicatedin Fig. 3. The spiral arrangement of the wire in each of the sevralconvolutions is indicated in Fig. 2, from hioh it will appear that theseveral turns of the spirals of the several convolutions of wire formingthe gromet lie side by side around the entire circumference of thegromet. y

' After the manufacture of the gromet in the form indicated in Fig. 3has been completed, the gromet is subjected to pressure to contract itscross-sectional size by taking up thespace at the center of the grometand the pressing devices employed for this purpose are such as to givethe gromet a triangular cross-sectional shape with the apex of thetriangle lying at the outer side of the gromet. This cross-sectionalshape of the grometis illustrated in Fig. 4, from which it appears thatthe central space within the gromet has been taken up and the severalconvolutions of the wire from which the gromet is formed are caused toassume positions wherein three wires lie abreast on the inner side ofthe gromet, two wires lie side by side and against these three, and asingle wire lies at the apex of the triangle. The

apex of the triangle is on the outer side of the gromet and at the innerside is one of the sides of the triangle? The spiralformation of all ofthe convolutions of the gromet iauses the six Wires tocome successivelyto he apex position and each of the other positions within the triangleindicated in Fig. 4, but notwithstanding this, the triangularcross-sectional shape of the 1gromet and the arrangement of the wires int e manner indicated in Fig. 4, is substantially maintained throughoutthe entire circumference of the gromet. Any suitable mechanism may beemployed for pressing the gromet from the cross-sectional shapeindicated in Fig. 3 to that indicated in Fig. 4. For instance, a pair ofrolls may be employed, one having a V-shaped circumferential groovetherein and the other having a flat periphery, means being provided forpressing the rolls together with the requisite force. The use of such amechanism may result in increasing the circumferential length of thegromet; ordinarily this would not be objectionable as the gromet wouldbe originally made of a size which would allow for this increase. Ifdesired, other forms of pressing mechanism may be employed, wherein thepressure is applied to all parts of the gromet simultaneously, thusavoiding any, increase in the circumferential length of the gromet.

It will be noted by reference to Figs. 3

and 4, that all of the six convolutions of spirally :formed wireconstituting the gromet as a whole lie upon the surface of the gromet.There is no convolution constituting a central core upon which the otherconvolutions are wound, as has been characteristic ofgroinetsheretoi'ore made. This characteristic of the gromet shown inFig. 8 permits ofpressing the gromet to the form illustrated in Fig. 4,which is particularly favorable to use of the gromet in themanufactureof automobile tires. The manufacture of gromets in the formindicated with all of the several convolutions lying upon he surface ismade possible by giving the wire constituting the several convolutionsits spiral formation and killing the metal of the wire so that it willhold its spiral formation, before applying the wire to the gromet, asdistinguished from giving. the

' substantially as described.

' 2. A gromet comprising the combination of a plurality of convolutions,each wound spirally, the gromet being formed from a continuous piece ofWire having its ends secured together and being of trian larcrosssection throughout; substantia ly as described.

3. A gromet consisting of six. convolutions of a continuous piece ofwire having its ends secured together, each convolution consisting of asuccession of spirals, and the gromet being substantially! triangular incross-section throughout and at each of a multiplicity of points havingthree convolutions lying side by side on the inner side of the gromet,one convolution lying at the apex of the triangle on the outer side ofthe gromet and the two remaining convolutions lying between them;substantially as described.

In testimony whereof I ailix my signature.

ALPHONSO COMSTOOK PRATT.

